One example of delivering a viscous material to a medical site is in a vertebroplasty procedure. Typically, the clinician seeks to treat a compression fracture of a vertebral body by injecting bone cement, a highly viscous material into a fracture site. In order to assure that the injected cement does not travel far from its intended placement location, fluoroscopy is often used by the clinician to monitor the location of the injected cement. However, delivering the cement by simple syringe would require the clinician to place his hand in the fluoroscopy field causing the clinician to be exposed to significant radiation produced by the fluoroscope during delivery of the cement to the surgical site. Thus, in order to reduce such exposure, the clinician often performs this procedure when the fluoro is turned off, and only monitors the cement location intermittently when safely outside the range of the fluoroscopy field.
Known techniques for keeping the clinician outside the fluoro field typically involve the use of a long extension tube, whereby one end of the tube extends from an injection pump and the other end is coupled to a hollow bone needle. The extension tube is used as a conduit for delivering the bone cement from the pump to the bone needle for injection into the vertebral body. The additional length of the extension tube allows a clinician to perform the vertebroplasty at a distance outside the fluoro field.
A disadvantage of such injection devices is that the cement is a highly viscous material requiring a high force to move the cement through the tube, resulting in a high-pressure build up within the device. The pressure build-up increases the effort need to inject the cement and decreases the natural feedback to the clinician. For example, the lack of natural feedback can cause the clinician to inadvertently leak bone cement into the surrounding tissue or the spinal cord itself, resulting in a number of serious health risks. Furthermore, the additional length of tube makes such injection devices susceptible to premature curing or hardening, resulting in the tube becoming clogged.